Electrokinetic heat pipe

ABSTRACT

A heat pipe for transporting a large quantity of heat within a small temperature difference provided with a tube, a wick, and a fluid that can transfer heat. The tube includes an evaporator section at one end and a condenser section at the opposite end thereof. The wick is disposed uniformly against the side walls of the tube and provides a capillary action to transfer the fluid from the condenser section to the evaporator section. Heat at the evaporator section causes the fluid to evaporate, wherein the vapor is then transmitted to the condenser section where the vapor condenses, thus giving up its latent heat, and is again transmitted to the evaporator section by the wick to define a continuous flow within the heat pipe. Electrodes are disposed within the tube, one electrode being disposed adjacent to the evaporator section, and the other electrode being disposed adjacent to the condenser section. When a potential difference is applied to the electrode, an electro-osmotic flow pumping is effected within the pipe, thereby, increasing the maximum heat capability of the heat pipe or overcoming any vapor lock present in the wick. Without the applied potential difference, the heat pipe functions as either an electrokinetic power generator or as a potential generator.

United States Patent Abu-Romia ELECTROKINETIC HEAT PIPE Inventor: Momtaz M. Abu-Romia, 124 Amity St., Brooklyn, NY. 11201 Filed: Feb. 25, 1971 Appl. No.: 118,756

References Cited UNITED STATES PATENTS 12/1968 Marks ..'...3l0/6 4/1969 Groveretal ..3l0/4 OTHER PUBLICATIONS Solion (Distributed by O.T.S. Dept. of Commerce), OD. 561, 115-1958 7 Primary ExaminerAlbert W. Davis, .Ir. Attorney-Friedman & Goodman [151 3,682,239 14 1 Aug. :8, 1972 ABSTRACT A heat pipe for transporting a large quantity of heat within a small temperature difference provided with a tube, a wick, and a fluid that can transfer heat. The tube includes an evaporator section at one end and a condenser section at the opposite end thereof. The wick is disposed uniformly against the side walls of the tube and provides a capillary action to transfer the fluid from the condenser section to the evaporator section. Heat at the evaporator section causes the fluid to evaporate, wherein the vapor is then transmitted to the condenser section where the vapor condenses, thus giving up its latent heat, and is again transmitted to the evaporator section by the wick to define a continuous'flow within the heat pipe. Electrodes are disposed within the tube, one electrode being disposed adjacent to the evaporator section, and the other electrode being disposed adjacent to the condenser section. When a potential difference is applied to the electrode, an electro-osmotic flow pumping is effected within the pipe, thereby, increasing the maximum heat capability of the heat pipe or overcoming any vapor lock present in the wick. Without the applied potential difference, the heat pipe functions as either an electrokinetic power generator or as a potential generator.

23 Claims, 3 Drawing Figures CONDENSER EVAPORATOR SECTION SECTION 4 4' I 4 ADIABATIC CONDENSER SECTION I I6 (/ZZO QUONOILWLNB ELM; 24 so (fl /O J{ ''UN1T z -34 2-.-- l 32 A. W Q .7.

BACKGROUND OF THE INVENTION Heat pipes are well known in the art. These heat pipes have a fraction of the weight, and several hundred times the heat transfer capability of solid copper, silver or aluminum. Heat pipes can replace many conduction heat-transfer systems, thereby improving performance of nearly any energy-conversion system. It is of considerable interest at the present time to find the maximum heat transferred by these heat pipes, and what modifications could be incorporated in the pipes to increase their heat capacity for given evaporator, condenser and wick parameters. It is recognized that the rate of heat transfer by-a heat pipe is limited by the capacity of its capillary pump and/or by the presence of I vapor lock in the wick at the evaporator section. The present invention considers the employment of electrodes in heat pipes for increasing its heat capacity,

overcoming the vapor lock in the wick, and for using the heat pipe as a generator.

SUMMARY OF THE INVENTION This invention relates to the art of transferring heat, and more particularly to a heat pipe for transferring heat from one point to another. The heat pipe comprises a tube, a wick within the tube, fluid that can transfer heat and electrodes disposed within the tube. The electrodes permit the heat pipe to function as a generator in one form of the invention. In another form of the invention, a potential difference is applied to the electrodes so that the heat pipe provides an electroosmotic flow pumping therein to increase the maximum heat capability of the heat pipe and to overcome any vapor lock present in the wick.

Accordingly, an object of the present invention is to provide a heat pipe for transporting a large quantity of heat which overcomes the disadvantages of the prior art.

tained for given evaporator, condenser and wick perameters.

A further object of this invention is to provide a heat pipe which overcomes any vapor lock present in the wick.

And a further object of this invention is to provide a heat pipe which includes electro-osmotic flow pumping therein.

A still further object of this invention is to provide a heat pipe provided with electrode means for starting up the pipe to reduce the transient period required in the prior art.

And yet a further object of this invention is to provide a heat pipe that functions as an electrokinetic power generator.

And yet a still further object of this invention is to provide a heat pipe that functions as a potential generator.

An added object of this invention is to provide a device that can transfer heat at a phenomenal rate which is simple, inexpensive and very reliable.

2 BRIEF DESCRIPTION OF THE DRAWINGS Having in mind the above and other objects that will be evident from an understanding of this disclosure, the invention comprises the devices, combinations and arrangements of parts as illustrated in the present preferred embodiments of the invention which is hereinafter set forth in such detail as to enable those skilled in the art readily to understand the function, operation, construction and advantages of it, when read in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic representation of a heat pipe according to the presentinvention featuring electroosmotic flow pumping;

FIG. 2 is a schematic representation of a heat pipe according to the present invention, functioning as an electrokinetic power generator; and

FIG. 3 is a schematic representation of a heat pipe according to the present invention functioning as a potential generator.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, FIG. 1 illustrates a heat pipe 10 of the present invention. The heat pipe 10 includes a tube 12 and a wick 14. The tube 12 defines a closed outer shell preferably provided with a circular cross-section, however, the tube may assume any desired geometric shape. The wick 14, which is a commercially available porous capillary wick, is held by conventional means uniformly against the inside walls of the tube 12 extending from one end portion 16 of the tube 12 to the opposite end portion 18 thereof. The end portion 16 defines the evaporator section and the end portion 18 defines the condenser section, as will be set forth in more detail hereinafter below.

A heating unit 20 is disposed on the evaporator section 16. The heating unit 20 is of the conventional type, such as a heating coil containing heated gases, fluids, solids, or thermal radiation at the evaporator section 16 so that the heat may be transferred therefrom. A conventional condenser cooling unit 22 is disposed on the condenser section 18 to remove the heat from the heat pipe 10. Conventional cooling fluids, such as water, may be used in the cooling unit 22 as indicated by the arrows in FIG. 1 to assist in the heat removal therefrom.

A fluid that can transfer at a phenomenal rate is disposed within the heat pipe 10. Many different types of liquids such as: benzene, gasoline and water solutions can be used as working fluids. It has been found that favorable results are achieved with dilute water solutions, such as distilled water in equilibrium with atmospheric carbon dioxide. The fluid is in the form of a liquid 24 when flowing in the wick l4, and in the form of a vapor 26 when flowing centrally within the tube 12 as set forth hereinafter below.

The function of the structure thus far described will now be set forth. The heat pipe 10, as shown in FIG. 1, is disposed at any angle 28 between 0 and from the vertical position. In operation, the liquid 24, due to the capillary action of the wick 14 will climb up through the porous capillary wick 14 to the upper portion of the tube 12 where it will evaporate under the higher temperatures to which this protion 16 of the tube 12 and the capillary wick 14 are subjected; the heat being added by the material contained within the heating unit 20. This evaporated liquid will collect in the form of the vapor 26 in the evaporator section 16, and by progressive accumulation therein, will be forced down through an adiabatic intermediate section 30 of the tube 12 to the bottom portion 18 of the tube 12. The vapor 26 will condense within the condenser section 18 to again form the liquid 24, wherein the cooling unit will remove the heat therefrom. The above process is again repeated so that a continuous flow is maintained. Thus, by this principle, the heat pipe transmits heat downwardly through evaporation and condensation, and raises liquid upwardly without the expenditure of any work in raising the liquid.

Accordingly, to increase the maximum heat capability of the heat pipe 10 and to overcome any vapor lock present in the wick 14, a pair of electrodes 32 and 34 are disposed within the heat pipe 10. The electrode 32 is disposed between the evaporator section 16 and the aidabatic section 30, with the electrode 34 being disposed at a lower portion of the condenser section 18. A potential difference from a conventional source 36 is applied to the electrodes 32, 34 through lines 40, 42 respectively.

Electrokinetic flow phenomena are dependent upon the presence of a naturally occurring potential, or a charge accumulation at the interface of the fluid and the capillary walls. The surface potential causes a redistribution of the charged ions present in the fluid, so that the movement of the fluid is thereby accompanied by a movement of charge. When the fluid is moved through a capillary element, an axial streaming potential gradient is generated which is directly proportional to the pressure gradient and to the electrokinetic mobility. Conversely, when an axial potential gradient is applied to the capillary element, flow is generated which is directly proportional to the potential gradient. The former phenomena is denoted as a streaming current generator and is associated with electrokinetic power generation as will be discussed hereinafter below. The latter phenomena is called electro-osmotic flow pumping and is utilized in connection with the heat pipe as 7 shown in FIG. 1.

The electrodes 32 and 34 provide an axial potential gradient within the heat pipe 10, being applied to the capillary wick 14. Both electrodes 32 and 34 are porous, with the electrode 34 being positively charged and the electrode 32 being negatively charged. With the presence at a net charge density within the wick, the axial potential gradient produced by the electrodes 32, 34 creates an electro-osmotic force which causes an increase in the flow of the liquid 24 towards the evaporator section 16. The increased flow between the electrodes 32, 34 is directly proportional to the applied potential from the source 36.

With the electrodes providing an electro-osmotic flow pumping, the angle 28 at which the heat pipe 10 is disposed can be zero whereby there still will be provided a continuous flow within the heat pipe 10, or any angle between 0 and 180 degrees, as stated above. Decreasing the capillary channel width of the wick 14 causes a greater charge density of the liquid 24 thereby increasing the flow and improving the efficiency of the heat pipe 10. Considerably higher efficiencies are attainable with the use of ultrafine tubular capillaries. The wick material can be glass, ilmenite, quartz, clay, foam, paper or any other suitable substance. Preferably, the wick material of the present invention is chosen to be glass beads based on the knowledge of the surface properties of glass in contact with a water solution. If a flexible heat pipe is desired, a flexible wick material such as fiberglass may be used. Preferably, the tube 12 is constructed of conventional dielectric materials, which are well known in the art.

The heat pipe 10 which is sealed or enclosed as shown in FIG. 1, has a quick starting up time because of the effect of the electro-osmotic pumping. Therefore, once the heat pipe 10 has been started up and a continuous flow is established, the applied potential from the source 36 may be disconnected from the heat pipe 10, wherein the heat pipe 10 will continue to operate as set forth above, however, at a lower heat capacity. Therefore, as shown above, the electro-osmotic pumping of the heat pipe 10 can be continuously used or used only for starting up the heat pipe to reduce the transient period thereof.

FIG. 2 illustrates a second embodiment of a heat pipe of the present invention wherein similar parts are denoted by similar reference numerals.

in this construction, a heat pipe 10A includes a tube 12A and a wick 14A having similar construction to tube 12 and wick 14 mentioned above. The tube 12A includes an end portion 16A defining an evaporator section, an intermediate portion 30A defining an adiabatic section, and an opposite end portion 18A defining a condenser section. A fluid similar to the above-mentioned fluid of heat pipe 10, is disposed within the heat pipe 10A so that a liquid 24A flows in the wick 14A and a vapor 26A flows centrally within the tube 12A in the space or passage provided therefor. The heat pipe 10A is disposed at a predetermined angle 28A between 0 and as stated above.

Accordingly, a pair of electrodes 32A and 34A are disposed within the heat pipe 10A. The electrode 32A is disposed between the evaporator section 16A and the adiabatic section 30A, with the electrode 34A being disposed at a lower portion of the condenser section 18A. Any one of a plurality of electrically operated objects 50 provided with a resistance 52 may be associated with the heat pipe 10A. The resistance 52 is connected in series through lines 40A and 42A to the electrodes 32A, 34A, respectively, in order to operate the object 50, as set forth hereinafter below.

The heat pipe 10A defines an electrokinetic power generator. As stated above, a naturally occurring potential is present within the heat pipe 10A, with a charge accumulation at the interface of the liquid 24A and the capillary walls of the wick 14A, causing a redistribution of the charged ions present in the liquid 24A. When the liquid 24A flows through the capillary wick 14A, there is also a movement of charge therethrough so that an axial streaming potential gradient is generated. Since the net charge density is often positive, fluid motion causes the porous electrodes 32A to be positively charged and the porous electrode 34A to be negatively charged, so that electrical power is generated to the resistance 52 of the object 50.

Rather than employing heating units, the evaporator section 16A is preferably heated by the sun. Preferably, the wick 14A is disposed uniformly against the side walls and end wall of the evaporator section 16A to increase the efiiciency of the heat pipe A. Additionally, rather than employing a condenser cooling unit, the condenser section 18A is air cooled with the condenser section 18A being shaded from the sun by conventional means (not shown).

In operation, the liquid 24A, due to the capillary action of the wick 14A, will climb up through the porous capillary wick 14A to the upper portion 16A of the tube 12A where it will evaporate under the higher temperatures to which this portion 16A of the tube 12A and the capillary wick 14A are subjected; the heat being obtained from the sun. This evaporated liquid will collect in the form of the vapor 26A in the evaporator section 16A, and by progressive accumulation therein, will be forced down through the passage in the adiabatic intermediate section 30A of the tube 12A to the bottom portion 18A of the tube 12A.

The vapor 26A will condense within the condenser section 18A to again form the liquid 24A, with the air disposed around the outer surface of the condenser section 18A removing the heat therefrom. The above process is again repeated so that a continuous flow is maintained, during which time the electrodes 32A and 34A are charged to supply electrical power to the object 50. It is obviously understood, that the heat pipe 10A will function equally as well with heating and cooling units as described above.

FIG. 3 illustrates a third embodiment of a heat pipe of the present invention, wherein similar parts are denoted by similar reference numerals.

In this construction, a heat pipe 10B includes a tube 12B and a wick 14B having similar construction to the tube 12 and the wick 14 mentioned above. The tube 128 includes an end portion 16B defining an evaporator section, an intermediate portion 30B defining an adiabatic section, and an opposite end portion 18B defining a condenser section. A fluid similar to the above-mentioned fluid of heat pipe 10, is disposed within the heat pipe 10B so that a liquid 24B flows in the wick 14B and a vapor 26B flows centrally within the tube 12B in the space or passage provided therefor. The heat pipe 108 is disposed at a predetermined angle 28B between 0 and 180, as stated above.

Accordingly, a pair of electrodes 32B and 34B are disposed within the heat pipe 103. Electrode 32B is disposed between the evaporator section 16B and the adiabatic section 30B, with the electrode 34B being disposed at a lower portion of the condenser section 18B. The electrode 32B and 34B have portions 33 and 35, respectively, extending outwardly from the outer surface of the tube 12B, the function of which will be set forth herein below.

The heat pipe 10B defines a potential generator. As stated above, a naturally occurring potential is present within the heat pipe 10B, with a charge accumulation at the interface of the liquid 24B and the capillary walls of the wick 14B, causing a redistribution of the charged ions present in the liquid 24B flows through the capillary wick 148, there is also a movement of charge therethrough so that an axial streaming potential gradient is generated. This axial streaming potential gradient causes the porous electrode 328 to be positively charged, and the porous electrode 34B to be negatively charged, so that a potential is effected between the outwardly extending portions 33 and 35 of the electrodes.

Rather than employing heat coils, the evaporator section 16B is heated by any conventional heat source 203. Additionally, rather than employing a condenser cooling unit 223 as shown in FIG. 3, any conventional cooling means may be used.

In operation, the liquid 24B, due to the capillary action of the wick 14B, will climb up through the porous capillary wick MB to the upper portion 163 at the tube 12B, where it will evaporate under the higher temperatures to which this portion 168 of the tube 12B and the capillary wick 14B are subjected; the heat being obtained from the heat source 208. This evapoated liquid will collect in the form of the vapor 26B in the evaporator section 16B, and by progressive accumulation therein, will be forced down through the passage in the adiabatic intermediate section 30B of the tube 12B to the bottom portion 183 of the tube 12B.

The vapor 26B will condense within the condenser section 18B to again form the liquid 248, where the condenser cooling unit 223 disposed around the outer surface of the condenser section 18B will remove the heat therefrom. The above process is again repeated so that a continuous flow is maintained, during which time the electrodes 32B and 34B are charged to efiect a potential between portions 33 and 35 of the electrodes.

It is noted that adiabatic sections 30, 30A and 30B transfer the heat from the evaporator sections to the condenser sections without any loss or gain of heat, thus simplifying its design and operation, and providing an unlimited number of practical applications thereof.

Numerous alterations of the structures herein disclosed will suggest themselves to those skilled in the art. As for example, in the absence of the adiabatic section of the heat pipe, both electrodes are to be embedded within the condenser section. lt is to be understood that the present disclosure relates to a preferred embodiment of the invention which is for the purpose of illustration only, and not to be construed as a limitation of the invention.

What is claimed is:

l. A heat transfer device comprising a body member, said body member including a first portion for receiving heat from a heat source and a second portion for transferring heat away from said body member, capillary means extending between said first and second portions, said body member being provided with a passage communicating with said first and second portions, a liquid associated with said capillary means, spaced apart electrode means disposed within said body member for cooperation with said capillary means, said electrode means being associated with a potential gradient functioning within said body member, and non-conductive means for isolating said spaced electrode means from one another within said body member.

2. A heat transfer device according to claim 1, wherein said capillary means includes a porous capillary wick disposed uniformly against inside walls of said body member.

3. A heat transfer device according to claim 1, wherein said body member includes a sealed tube, said first portion defining an evaporator section and said second portion defining a condenser section.

4. A heat transfer device according to claim 3, wherein an adiabatic section of said tube is disposed between said evaporator and condenser sections.

5. A heat transfer device according to claim 3, wherein a heat source is disposed adjacent to said evaporator section.

6. A heat transfer device according to claim 5, wherein said heat source includes a heating unit disposed around said evaporator section.

7. a heat transfer device according to claim 3, wherein cooling means are disposed adjacent to said condenser section.

8. A heat transfer device according to claim 7, wherein said cooling means include a condenser cooling unit disposed around said condenser section.

9. A heat transfer device according to claim 1, wherein said body members are disposed at a predetermined angle between and 180 fromvertical position.

10. A heat transfer device according to claim 1, wherein said electrode means includes a first electrode associated with and disposed adjacent to said first portion, and a second electrode associated with and disposed adjacent to said second portion.

11. A heat transfer device according to claim 10, wherein a potential difference is applied to said first and second electrodes to provide said potential gradient to produce electro-osmotic flow pumping.

12. A heat transfer device according to claim 11, wherein said body member is disposed at 0 with reference to vertical position.

13. A heat transfer device according to claim 10, wherein said potential gradient produces a potential difference between said first and second electrodes to provide a generator.

14. A heat transfer device according to claim 13, wherein a resistance is disposed inseries with said first and second electrodes to effect an electrokinetic power generator.

15. A heat transfer device according to claim 13, wherein portions of said first and second electrodes extend outwardly from said body member to effect a potential generator.

16. A method of transferring heat from a first point at a higher temperature to a second point at a lower temperature employing a device containing a liquid, said method comprising evaporating the liquid at the first point to form a vapor, condensing the vapor at the second point, returning by capillary action the condenser liquid from the second point to the first point, and applying a potential gradient to the returning condensed liquid.

17. A method according to claim 16, wherein a first electrode is disposed adjacent to said first point, a second electrode is disposed adjacent to said second point, and a potential difference is applied to said first and second potential to provide said potential gradient to produce electro-osmotic flow pumping.

18. A method according to claim 17, wherein a heat source is disposed at said first point to provide said higher temperature, and cooling means are disposed at fsi fili rlr lbfusifgffiil fiiiililfill iia to transfer heat from a first point at a higher temperature toa second point at a lower temperature for producing a generator, said method comprising evaporating the liquid at the first point to form a vapor, condensing the vapor at the second point, returning by capillary action the condensed liquid from the second point to the first point, and producing a potential gradient associated with the movement of the returning condensed liquid.

20. A method according to claim 19, wherein a first electrode is disposed adjacent to said first point, a second electrode is disposed adjacent to said second point, said potential gradient providing a potential difference between said first and second electrodes to produce said generator.

21. A method according to claim 20, wherein a resistance is disposed in series with said first and second electrodes to produce an electrokinetic power generator.

22. A method according to claim 20, wherein said first and second electrodes are extended outwardly from said device to produce a potential generator.

23. A method according to claim 20, wherein a heat source is disposed at said first point to provide said higher temperature, and cooling means are disposed at said second point to provide said lower temperature. 

1. A heat transfer device comprising a body member, said body member including a first portion for receiving heat from a heat source and a second portion for transferring heat away from said body member, capillary means extending between said first and second portions, said body member being provided with a passage communicating with said first and second portions, a liquid associated with said capillary means, spaced apart electrode means disposed within said body member for cooperation with said capillary means, said electrode means being associated with a potential gradient functioning within said body member, and nonconductive means for isolating said spaced electrode means from one another within said body member.
 2. A heat transfer device according to claim 1, wherein said capillary means includes a porous capillary wick disposed uniformly against inside walls of said body member.
 3. A heat transfer device according to claim 1, wherein said body member includes a sealed tube, said first portion defining an evaporator section and said second portion defining a condenser section.
 4. A heat transfer device according to claim 3, wherein an adiabatic section of said tube is disposed between said evaporator and condenser sections.
 5. A heat transfer device according to claim 3, wherein a heat source is disposed adjacent to said evaporator section.
 6. A heat transfer device according to claim 5, wherein said heat source includes a heating unit disposed around said evaporator section.
 7. a heat transfer device according to claim 3, wherein cooling means are disposed adjacent to said condenser section.
 8. A heat transfer device according to claim 7, wherein said cooling means include a condenser cooling unit disposed around said condenser section.
 9. A heat transfer device according to claim 1, wherein said body members are disposed at a predetermined angle between 0* and 180* from vertical position.
 10. A heat transfer device according to claim 1, wherein said electrode means includes a first electrode associated with and disposed adjacent to said first portion, and a second electrode associated with and disposed adjacent to said second portion.
 11. A heat transfer device according to claim 10, wherein a potential difference is applied to said first and second electrodes to provide said potential gradient to produce electro-osmotic flow pumping.
 12. A heat transfer device according to claim 11, wherein said body member is disposed at 0* with reference to vertical position.
 13. A heat transfer device according to claim 10, wherein said potential gradient produces a potential difference between said first and second electrodes to provide a generator.
 14. A heat transfer device according to claim 13, wherein a resistance is disposed inseries with said first and second electrodes to effect an electrokinetic power generator.
 15. A heat transfer device according to claim 13, wherein portions of said first and second electrodes extend outwardly from said body member to effect a potential generator.
 16. A method of transferring heat from a first point at a higher temperature to a second point at a lower temperature employing a device containing a liquid, said method comprising evaporating the liquid at the first point to form a vapor, condensing the vapor at the second point, returning by capillary action the condenser liquid from the second point to the first point, and applying a potential gradient to the returning condensed liquid.
 17. A method according to claim 16, wherein a first electrode is disposed adjacent to said first point, a second electrode is disposed adjacent to said second point, and a potential difference is applied to said first and second potential to provide said potential gradient to produce electro-osmotic flow pumping.
 18. A method according to claim 17, wherein a heat source is disposed at said first point to provide said higher temperature, and cooling means are disposed at said second point to provide said lower temperature.
 19. A method of using a device containing a liquid to transfer heat from a first point at a higher temperature to a second point at a lower temperature for producing a generator, said method comprising evaporating the liquid at the first point to form a vapor, condensing the vapor at the second point, returning by capillary action the condensed liquid from the second point to the first point, and producing a potential gradient associated with the movement of the returning condensed liquid.
 20. A method according to claim 19, wherein a first electrode is disposed adjacent to said first point, a second electrode is disposed adjacent to said second point, said potential gradient providing a potential difference between said first and second electrodes to produce said generator.
 21. A method according to claim 20, wherein a resistance is disposed in series with said first and second electrodes to produce an electrokinetic power generator.
 22. A method according to claim 20, wherein said first and second electrodes are extended outwardly from said device to produce a potential generator.
 23. A method according to claim 20, wherein a heat source is disposed at said first point to provide said higher temperature, and cooling means are disposed at said second point to provide said lower temperature. 